I intend to harvest substantial amounts of LDL receptors from human aortic intima and from human skin fibroblasts. These preparations, purified by affinity chromatography, will be labeled with 125I and then subjected to SDS acrylamide gel electrophoresis, in order to compare the respective migration patterns. At the moment, it is not known whether the two receptors preparations are identidcal or not. I will also use each one of these preparations for the production of monoclonal antibodies. Once these will be available, they will be used to evaluate the possible immunological differences between the two receptor preparations. Moreover, these antibodies will be used to detect the presence of LDL receptors in various cultured cells to evaluate the distribution of these receptors on different areas of human aortic intima.